A preferred type of alternating current voltage regulator known in the art chops the supply voltage waveform at a frequency substantially higher than that of the supply voltage. Such a regulator is set forth in U.S. Pat. No. 3,564,394, issued to K. E. Opal et al., on Feb. 16, 1971. However, noise generated by the chopping causes problems when such supplies are used in communication systems, control systems, computer systems and others susceptible to noises caused by discontinuities, cusps and resulting harmonics introduced by the chopping.
Another technique, as set forth in U.S. Pat. No. 2,007,519, issued to J. J. Smith, on July 16, 1935, or U.S. Pat. No. 1,873,952, issued to E. Aubort, Aug. 30, 1932, provides for the generation of specific harmonics and controlling the amplitude and phase for adding to and cancelling out those harmonics in the output of the voltage supply.
Active type filters are also known to reduce harmonics in power converter systems as set forth in U.S. Pat. No. 4,358,818, issued to J. Rosa, Nov. 9, 1982 or U.S. Pat. No. 3,825,814, issued to B. R. Pelly, July 23, 1974.
In all of these prior art techniques it is extremely difficult to match and eliminate all the spurious noises and harmonics, and the best that can be expected is to eliminate those components that provide the major noise interference problems.
It is accordingly an objective of this invention to improve the state of the art by a more thorough elimination of a range of harmonic and spurious noise signals in a chopped waveform type of power supply system.